/*
 * Copyright (C) 2008 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
 * in compliance with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */

package com.google.common.primitives;

import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkElementIndex;
import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.base.Preconditions.checkPositionIndexes;
import static com.google.common.base.Strings.lenientFormat;
import static java.lang.Double.NEGATIVE_INFINITY;
import static java.lang.Double.POSITIVE_INFINITY;

import com.google.common.annotations.Beta;
import com.google.common.annotations.GwtCompatible;
import com.google.common.annotations.GwtIncompatible;
import com.google.common.base.Converter;

import java.io.Serializable;
import java.util.AbstractList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
import java.util.RandomAccess;
import java.util.Spliterator;
import java.util.Spliterators;
import javax.annotation.CheckForNull;

/**
 * Static utility methods pertaining to {@code double} primitives, that are not already found in
 * either {@link Double} or {@link Arrays}.
 *
 * <p>See the Guava User Guide article on <a
 * href="https://github.com/google/guava/wiki/PrimitivesExplained">primitive utilities</a>.
 *
 * @author Kevin Bourrillion
 * @since 1.0
 */
@GwtCompatible(emulated = true)
@ElementTypesAreNonnullByDefault
public final class Doubles extends DoublesMethodsForWeb
{
    private Doubles()
    {
    }

    /**
     * The number of bytes required to represent a primitive {@code double} value.
     *
     * <p><b>Java 8 users:</b> use {@link Double#BYTES} instead.
     *
     * @since 10.0
     */
    public static final int BYTES = Double.SIZE / Byte.SIZE;

    /**
     * Returns a hash code for {@code value}; equal to the result of invoking {@code ((Double)
     * value).hashCode()}.
     *
     * <p><b>Java 8 users:</b> use {@link Double#hashCode(double)} instead.
     *
     * @param value a primitive {@code double} value
     * @return a hash code for the value
     */
    public static int hashCode(double value)
    {
        return ((Double) value).hashCode();
        // TODO(kevinb): do it this way when we can (GWT problem):
        // long bits = Double.doubleToLongBits(value);
        // return (int) (bits ^ (bits >>> 32));
    }

    /**
     * Compares the two specified {@code double} values. The sign of the value returned is the same as
     * that of <code>((Double) a).{@linkplain Double#compareTo compareTo}(b)</code>. As with that
     * method, {@code NaN} is treated as greater than all other values, and {@code 0.0 > -0.0}.
     *
     * <p><b>Note:</b> this method simply delegates to the JDK method {@link Double#compare}. It is
     * provided for consistency with the other primitive types, whose compare methods were not added
     * to the JDK until JDK 7.
     *
     * @param a the first {@code double} to compare
     * @param b the second {@code double} to compare
     * @return a negative value if {@code a} is less than {@code b}; a positive value if {@code a} is
     * greater than {@code b}; or zero if they are equal
     */
    public static int compare(double a, double b)
    {
        return Double.compare(a, b);
    }

    /**
     * Returns {@code true} if {@code value} represents a real number. This is equivalent to, but not
     * necessarily implemented as, {@code !(Double.isInfinite(value) || Double.isNaN(value))}.
     *
     * <p><b>Java 8 users:</b> use {@link Double#isFinite(double)} instead.
     *
     * @since 10.0
     */
    public static boolean isFinite(double value)
    {
        return NEGATIVE_INFINITY < value && value < POSITIVE_INFINITY;
    }

    /**
     * Returns {@code true} if {@code target} is present as an element anywhere in {@code array}. Note
     * that this always returns {@code false} when {@code target} is {@code NaN}.
     *
     * @param array  an array of {@code double} values, possibly empty
     * @param target a primitive {@code double} value
     * @return {@code true} if {@code array[i] == target} for some value of {@code i}
     */
    public static boolean contains(double[] array, double target)
    {
        for (double value : array)
        {
            if (value == target)
            {
                return true;
            }
        }
        return false;
    }

    /**
     * Returns the index of the first appearance of the value {@code target} in {@code array}. Note
     * that this always returns {@code -1} when {@code target} is {@code NaN}.
     *
     * @param array  an array of {@code double} values, possibly empty
     * @param target a primitive {@code double} value
     * @return the least index {@code i} for which {@code array[i] == target}, or {@code -1} if no
     * such index exists.
     */
    public static int indexOf(double[] array, double target)
    {
        return indexOf(array, target, 0, array.length);
    }

    // TODO(kevinb): consider making this public
    private static int indexOf(double[] array, double target, int start, int end)
    {
        for (int i = start; i < end; i++)
        {
            if (array[i] == target)
            {
                return i;
            }
        }
        return -1;
    }

    /**
     * Returns the start position of the first occurrence of the specified {@code target} within
     * {@code array}, or {@code -1} if there is no such occurrence.
     *
     * <p>More formally, returns the lowest index {@code i} such that {@code Arrays.copyOfRange(array,
     * i, i + target.length)} contains exactly the same elements as {@code target}.
     *
     * <p>Note that this always returns {@code -1} when {@code target} contains {@code NaN}.
     *
     * @param array  the array to search for the sequence {@code target}
     * @param target the array to search for as a sub-sequence of {@code array}
     */
    public static int indexOf(double[] array, double[] target)
    {
        checkNotNull(array, "array");
        checkNotNull(target, "target");
        if (target.length == 0)
        {
            return 0;
        }

        outer:
        for (int i = 0; i < array.length - target.length + 1; i++)
        {
            for (int j = 0; j < target.length; j++)
            {
                if (array[i + j] != target[j])
                {
                    continue outer;
                }
            }
            return i;
        }
        return -1;
    }

    /**
     * Returns the index of the last appearance of the value {@code target} in {@code array}. Note
     * that this always returns {@code -1} when {@code target} is {@code NaN}.
     *
     * @param array  an array of {@code double} values, possibly empty
     * @param target a primitive {@code double} value
     * @return the greatest index {@code i} for which {@code array[i] == target}, or {@code -1} if no
     * such index exists.
     */
    public static int lastIndexOf(double[] array, double target)
    {
        return lastIndexOf(array, target, 0, array.length);
    }

    // TODO(kevinb): consider making this public
    private static int lastIndexOf(double[] array, double target, int start, int end)
    {
        for (int i = end - 1; i >= start; i--)
        {
            if (array[i] == target)
            {
                return i;
            }
        }
        return -1;
    }

    /**
     * Returns the least value present in {@code array}, using the same rules of comparison as {@link
     * Math#min(double, double)}.
     *
     * @param array a <i>nonempty</i> array of {@code double} values
     * @return the value present in {@code array} that is less than or equal to every other value in
     * the array
     * @throws IllegalArgumentException if {@code array} is empty
     */
    @GwtIncompatible(
            "Available in GWT! Annotation is to avoid conflict with GWT specialization of base class.")
    public static double min(double... array)
    {
        checkArgument(array.length > 0);
        double min = array[0];
        for (int i = 1; i < array.length; i++)
        {
            min = Math.min(min, array[i]);
        }
        return min;
    }

    /**
     * Returns the greatest value present in {@code array}, using the same rules of comparison as
     * {@link Math#max(double, double)}.
     *
     * @param array a <i>nonempty</i> array of {@code double} values
     * @return the value present in {@code array} that is greater than or equal to every other value
     * in the array
     * @throws IllegalArgumentException if {@code array} is empty
     */
    @GwtIncompatible(
            "Available in GWT! Annotation is to avoid conflict with GWT specialization of base class.")
    public static double max(double... array)
    {
        checkArgument(array.length > 0);
        double max = array[0];
        for (int i = 1; i < array.length; i++)
        {
            max = Math.max(max, array[i]);
        }
        return max;
    }

    /**
     * Returns the value nearest to {@code value} which is within the closed range {@code [min..max]}.
     *
     * <p>If {@code value} is within the range {@code [min..max]}, {@code value} is returned
     * unchanged. If {@code value} is less than {@code min}, {@code min} is returned, and if {@code
     * value} is greater than {@code max}, {@code max} is returned.
     *
     * @param value the {@code double} value to constrain
     * @param min   the lower bound (inclusive) of the range to constrain {@code value} to
     * @param max   the upper bound (inclusive) of the range to constrain {@code value} to
     * @throws IllegalArgumentException if {@code min > max}
     * @since 21.0
     */
    @Beta
    public static double constrainToRange(double value, double min, double max)
    {
        // avoid auto-boxing by not using Preconditions.checkArgument(); see Guava issue 3984
        // Reject NaN by testing for the good case (min <= max) instead of the bad (min > max).
        if (min <= max)
        {
            return Math.min(Math.max(value, min), max);
        }
        throw new IllegalArgumentException(
                lenientFormat("min (%s) must be less than or equal to max (%s)", min, max));
    }

    /**
     * Returns the values from each provided array combined into a single array. For example, {@code
     * concat(new double[] {a, b}, new double[] {}, new double[] {c}} returns the array {@code {a, b,
     * c}}.
     *
     * @param arrays zero or more {@code double} arrays
     * @return a single array containing all the values from the source arrays, in order
     */
    public static double[] concat(double[]... arrays)
    {
        int length = 0;
        for (double[] array : arrays)
        {
            length += array.length;
        }
        double[] result = new double[length];
        int pos = 0;
        for (double[] array : arrays)
        {
            System.arraycopy(array, 0, result, pos, array.length);
            pos += array.length;
        }
        return result;
    }

    private static final class DoubleConverter extends Converter<String, Double>
            implements Serializable
    {
        static final DoubleConverter INSTANCE = new DoubleConverter();

        @Override
        protected Double doForward(String value)
        {
            return Double.valueOf(value);
        }

        @Override
        protected String doBackward(Double value)
        {
            return value.toString();
        }

        @Override
        public String toString()
        {
            return "Doubles.stringConverter()";
        }

        private Object readResolve()
        {
            return INSTANCE;
        }

        private static final long serialVersionUID = 1;
    }

    /**
     * Returns a serializable converter object that converts between strings and doubles using {@link
     * Double#valueOf} and {@link Double#toString()}.
     *
     * @since 16.0
     */
    @Beta
    public static Converter<String, Double> stringConverter()
    {
        return DoubleConverter.INSTANCE;
    }

    /**
     * Returns an array containing the same values as {@code array}, but guaranteed to be of a
     * specified minimum length. If {@code array} already has a length of at least {@code minLength},
     * it is returned directly. Otherwise, a new array of size {@code minLength + padding} is
     * returned, containing the values of {@code array}, and zeroes in the remaining places.
     *
     * @param array     the source array
     * @param minLength the minimum length the returned array must guarantee
     * @param padding   an extra amount to "grow" the array by if growth is necessary
     * @return an array containing the values of {@code array}, with guaranteed minimum length {@code
     * minLength}
     * @throws IllegalArgumentException if {@code minLength} or {@code padding} is negative
     */
    public static double[] ensureCapacity(double[] array, int minLength, int padding)
    {
        checkArgument(minLength >= 0, "Invalid minLength: %s", minLength);
        checkArgument(padding >= 0, "Invalid padding: %s", padding);
        return (array.length < minLength) ? Arrays.copyOf(array, minLength + padding) : array;
    }

    /**
     * Returns a string containing the supplied {@code double} values, converted to strings as
     * specified by {@link Double#toString(double)}, and separated by {@code separator}. For example,
     * {@code join("-", 1.0, 2.0, 3.0)} returns the string {@code "1.0-2.0-3.0"}.
     *
     * <p>Note that {@link Double#toString(double)} formats {@code double} differently in GWT
     * sometimes. In the previous example, it returns the string {@code "1-2-3"}.
     *
     * @param separator the text that should appear between consecutive values in the resulting string
     *                  (but not at the start or end)
     * @param array     an array of {@code double} values, possibly empty
     */
    public static String join(String separator, double... array)
    {
        checkNotNull(separator);
        if (array.length == 0)
        {
            return "";
        }

        // For pre-sizing a builder, just get the right order of magnitude
        StringBuilder builder = new StringBuilder(array.length * 12);
        builder.append(array[0]);
        for (int i = 1; i < array.length; i++)
        {
            builder.append(separator).append(array[i]);
        }
        return builder.toString();
    }

    /**
     * Returns a comparator that compares two {@code double} arrays <a
     * href="http://en.wikipedia.org/wiki/Lexicographical_order">lexicographically</a>. That is, it
     * compares, using {@link #compare(double, double)}), the first pair of values that follow any
     * common prefix, or when one array is a prefix of the other, treats the shorter array as the
     * lesser. For example, {@code [] < [1.0] < [1.0, 2.0] < [2.0]}.
     *
     * <p>The returned comparator is inconsistent with {@link Object#equals(Object)} (since arrays
     * support only identity equality), but it is consistent with {@link Arrays#equals(double[],
     * double[])}.
     *
     * @since 2.0
     */
    public static Comparator<double[]> lexicographicalComparator()
    {
        return LexicographicalComparator.INSTANCE;
    }

    private enum LexicographicalComparator implements Comparator<double[]>
    {
        INSTANCE;

        @Override
        public int compare(double[] left, double[] right)
        {
            int minLength = Math.min(left.length, right.length);
            for (int i = 0; i < minLength; i++)
            {
                int result = Double.compare(left[i], right[i]);
                if (result != 0)
                {
                    return result;
                }
            }
            return left.length - right.length;
        }

        @Override
        public String toString()
        {
            return "Doubles.lexicographicalComparator()";
        }
    }

    /**
     * Sorts the elements of {@code array} in descending order.
     *
     * <p>Note that this method uses the total order imposed by {@link Double#compare}, which treats
     * all NaN values as equal and 0.0 as greater than -0.0.
     *
     * @since 23.1
     */
    public static void sortDescending(double[] array)
    {
        checkNotNull(array);
        sortDescending(array, 0, array.length);
    }

    /**
     * Sorts the elements of {@code array} between {@code fromIndex} inclusive and {@code toIndex}
     * exclusive in descending order.
     *
     * <p>Note that this method uses the total order imposed by {@link Double#compare}, which treats
     * all NaN values as equal and 0.0 as greater than -0.0.
     *
     * @since 23.1
     */
    public static void sortDescending(double[] array, int fromIndex, int toIndex)
    {
        checkNotNull(array);
        checkPositionIndexes(fromIndex, toIndex, array.length);
        Arrays.sort(array, fromIndex, toIndex);
        reverse(array, fromIndex, toIndex);
    }

    /**
     * Reverses the elements of {@code array}. This is equivalent to {@code
     * Collections.reverse(Doubles.asList(array))}, but is likely to be more efficient.
     *
     * @since 23.1
     */
    public static void reverse(double[] array)
    {
        checkNotNull(array);
        reverse(array, 0, array.length);
    }

    /**
     * Reverses the elements of {@code array} between {@code fromIndex} inclusive and {@code toIndex}
     * exclusive. This is equivalent to {@code
     * Collections.reverse(Doubles.asList(array).subList(fromIndex, toIndex))}, but is likely to be
     * more efficient.
     *
     * @throws IndexOutOfBoundsException if {@code fromIndex < 0}, {@code toIndex > array.length}, or
     *                                   {@code toIndex > fromIndex}
     * @since 23.1
     */
    public static void reverse(double[] array, int fromIndex, int toIndex)
    {
        checkNotNull(array);
        checkPositionIndexes(fromIndex, toIndex, array.length);
        for (int i = fromIndex, j = toIndex - 1; i < j; i++, j--)
        {
            double tmp = array[i];
            array[i] = array[j];
            array[j] = tmp;
        }
    }

    /**
     * Returns an array containing each value of {@code collection}, converted to a {@code double}
     * value in the manner of {@link Number#doubleValue}.
     *
     * <p>Elements are copied from the argument collection as if by {@code collection.toArray()}.
     * Calling this method is as thread-safe as calling that method.
     *
     * @param collection a collection of {@code Number} instances
     * @return an array containing the same values as {@code collection}, in the same order, converted
     * to primitives
     * @throws NullPointerException if {@code collection} or any of its elements is null
     * @since 1.0 (parameter was {@code Collection<Double>} before 12.0)
     */
    public static double[] toArray(Collection<? extends Number> collection)
    {
        if (collection instanceof DoubleArrayAsList)
        {
            return ((DoubleArrayAsList) collection).toDoubleArray();
        }

        Object[] boxedArray = collection.toArray();
        int len = boxedArray.length;
        double[] array = new double[len];
        for (int i = 0; i < len; i++)
        {
            // checkNotNull for GWT (do not optimize)
            array[i] = ((Number) checkNotNull(boxedArray[i])).doubleValue();
        }
        return array;
    }

    /**
     * Returns a fixed-size list backed by the specified array, similar to {@link
     * Arrays#asList(Object[])}. The list supports {@link List#set(int, Object)}, but any attempt to
     * set a value to {@code null} will result in a {@link NullPointerException}.
     *
     * <p>The returned list maintains the values, but not the identities, of {@code Double} objects
     * written to or read from it. For example, whether {@code list.get(0) == list.get(0)} is true for
     * the returned list is unspecified.
     *
     * <p>The returned list may have unexpected behavior if it contains {@code NaN}, or if {@code NaN}
     * is used as a parameter to any of its methods.
     *
     * <p><b>Note:</b> when possible, you should represent your data as an {@link
     * ImmutableDoubleArray} instead, which has an {@link ImmutableDoubleArray#asList asList} view.
     *
     * @param backingArray the array to back the list
     * @return a list view of the array
     */
    public static List<Double> asList(double... backingArray)
    {
        if (backingArray.length == 0)
        {
            return Collections.emptyList();
        }
        return new DoubleArrayAsList(backingArray);
    }

    @GwtCompatible
    private static class DoubleArrayAsList extends AbstractList<Double>
            implements RandomAccess, Serializable
    {
        final double[] array;
        final int start;
        final int end;

        DoubleArrayAsList(double[] array)
        {
            this(array, 0, array.length);
        }

        DoubleArrayAsList(double[] array, int start, int end)
        {
            this.array = array;
            this.start = start;
            this.end = end;
        }

        @Override
        public int size()
        {
            return end - start;
        }

        @Override
        public boolean isEmpty()
        {
            return false;
        }

        @Override
        public Double get(int index)
        {
            checkElementIndex(index, size());
            return array[start + index];
        }

        @Override
        public Spliterator.OfDouble spliterator()
        {
            return Spliterators.spliterator(array, start, end, 0);
        }

        @Override
        public boolean contains(@CheckForNull Object target)
        {
            // Overridden to prevent a ton of boxing
            return (target instanceof Double)
                    && Doubles.indexOf(array, (Double) target, start, end) != -1;
        }

        @Override
        public int indexOf(@CheckForNull Object target)
        {
            // Overridden to prevent a ton of boxing
            if (target instanceof Double)
            {
                int i = Doubles.indexOf(array, (Double) target, start, end);
                if (i >= 0)
                {
                    return i - start;
                }
            }
            return -1;
        }

        @Override
        public int lastIndexOf(@CheckForNull Object target)
        {
            // Overridden to prevent a ton of boxing
            if (target instanceof Double)
            {
                int i = Doubles.lastIndexOf(array, (Double) target, start, end);
                if (i >= 0)
                {
                    return i - start;
                }
            }
            return -1;
        }

        @Override
        public Double set(int index, Double element)
        {
            checkElementIndex(index, size());
            double oldValue = array[start + index];
            // checkNotNull for GWT (do not optimize)
            array[start + index] = checkNotNull(element);
            return oldValue;
        }

        @Override
        public List<Double> subList(int fromIndex, int toIndex)
        {
            int size = size();
            checkPositionIndexes(fromIndex, toIndex, size);
            if (fromIndex == toIndex)
            {
                return Collections.emptyList();
            }
            return new DoubleArrayAsList(array, start + fromIndex, start + toIndex);
        }

        @Override
        public boolean equals(@CheckForNull Object object)
        {
            if (object == this)
            {
                return true;
            }
            if (object instanceof DoubleArrayAsList)
            {
                DoubleArrayAsList that = (DoubleArrayAsList) object;
                int size = size();
                if (that.size() != size)
                {
                    return false;
                }
                for (int i = 0; i < size; i++)
                {
                    if (array[start + i] != that.array[that.start + i])
                    {
                        return false;
                    }
                }
                return true;
            }
            return super.equals(object);
        }

        @Override
        public int hashCode()
        {
            int result = 1;
            for (int i = start; i < end; i++)
            {
                result = 31 * result + Doubles.hashCode(array[i]);
            }
            return result;
        }

        @Override
        public String toString()
        {
            StringBuilder builder = new StringBuilder(size() * 12);
            builder.append('[').append(array[start]);
            for (int i = start + 1; i < end; i++)
            {
                builder.append(", ").append(array[i]);
            }
            return builder.append(']').toString();
        }

        double[] toDoubleArray()
        {
            return Arrays.copyOfRange(array, start, end);
        }

        private static final long serialVersionUID = 0;
    }

    /**
     * This is adapted from the regex suggested by {@link Double#valueOf(String)} for prevalidating
     * inputs. All valid inputs must pass this regex, but it's semantically fine if not all inputs
     * that pass this regex are valid -- only a performance hit is incurred, not a semantics bug.
     */
    @GwtIncompatible // regular expressions
    static final
    java.util.regex.Pattern
            FLOATING_POINT_PATTERN = fpPattern();

    @GwtIncompatible // regular expressions
    private static java.util.regex.Pattern
    fpPattern()
    {
        /*
         * We use # instead of * for possessive quantifiers. This lets us strip them out when building
         * the regex for RE2 (which doesn't support them) but leave them in when building it for
         * java.util.regex (where we want them in order to avoid catastrophic backtracking).
         */
        String decimal = "(?:\\d+#(?:\\.\\d*#)?|\\.\\d+#)";
        String completeDec = decimal + "(?:[eE][+-]?\\d+#)?[fFdD]?";
        String hex = "(?:[0-9a-fA-F]+#(?:\\.[0-9a-fA-F]*#)?|\\.[0-9a-fA-F]+#)";
        String completeHex = "0[xX]" + hex + "[pP][+-]?\\d+#[fFdD]?";
        String fpPattern = "[+-]?(?:NaN|Infinity|" + completeDec + "|" + completeHex + ")";
        fpPattern =
                fpPattern.replace(
                        "#",
                        "+"
                );
        return
                java.util.regex.Pattern
                        .compile(fpPattern);
    }

    /**
     * Parses the specified string as a double-precision floating point value. The ASCII character
     * {@code '-'} (<code>'&#92;u002D'</code>) is recognized as the minus sign.
     *
     * <p>Unlike {@link Double#parseDouble(String)}, this method returns {@code null} instead of
     * throwing an exception if parsing fails. Valid inputs are exactly those accepted by {@link
     * Double#valueOf(String)}, except that leading and trailing whitespace is not permitted.
     *
     * <p>This implementation is likely to be faster than {@code Double.parseDouble} if many failures
     * are expected.
     *
     * @param string the string representation of a {@code double} value
     * @return the floating point value represented by {@code string}, or {@code null} if {@code
     * string} has a length of zero or cannot be parsed as a {@code double} value
     * @throws NullPointerException if {@code string} is {@code null}
     * @since 14.0
     */
    @Beta
    @GwtIncompatible // regular expressions
    @CheckForNull
    public static Double tryParse(String string)
    {
        if (FLOATING_POINT_PATTERN.matcher(string).matches())
        {
            // TODO(lowasser): could be potentially optimized, but only with
            // extensive testing
            try
            {
                return Double.parseDouble(string);
            }
            catch (NumberFormatException e)
            {
                // Double.parseDouble has changed specs several times, so fall through
                // gracefully
            }
        }
        return null;
    }
}
